Beam Failure Recovery RA Type Selection via RSRP Thresholds
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Solution Overview
Problem
Current wireless communication systems, particularly 5G NR, face challenges in efficiently performing Beam Failure Recovery (BFR) due to the lack of effective methods for handling beam failures, which can lead to service disruptions and reduced network performance.
Innovation Solution
The implementation of a method for User Equipment (UE) to detect beam failures and initiate a Random Access (RA) procedure using either a 2-step or 4-step RA type based on Reference Signal Received Power (RSRP) values, with the option to skip RA type selection if configured with Contention-Free RA (CFRA) resources, ensuring optimal beam recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE performs RA type selection based on RSRP values for beam failure recovery, then the reliability of beam recovery is improved, but the complexity of the RA procedure increases
Solution Approach 1:
The network configures the UE with multiple RA type indicators (first RA type indicator for 2-step RA, second RA type indicator for 4-step RA) in advance through RRC signaling. These indicators are prepared beforehand and associated with different SSBs or CSI-RSs, so when beam failure occurs, the UE can directly select the appropriate pre-configured RA type based on the detected reference signal, avoiding complex real-time decision-making and reducing procedural complexity while maintaining high reliability
Solution Approach 2:
The network provides feedback to the UE through RSRP thresholds and RA type indicators, guiding the UE's RA type selection. The UE measures the RSRP of downlink reference signals and compares it with configured thresholds to determine which pre-configured RA type to use. This feedback mechanism enables reliable beam recovery through configured indicators while simplifying the UE's decision process
2Productivity
If the UE skips RA type selection when configured with CFRA resources, then the RA procedure efficiency is improved, but the adaptability to different channel conditions is reduced
Solution Approach 1:
The RA resources are segmented into different types (CFRA and CBRA) with different RA type indicators configured for each. When CFRA resources are available, the UE uses the first RA type indicator for efficient recovery. When CFRA is not available or channel conditions deteriorate, the UE can fall back to using the second RA type indicator with CBRA resources. This segmentation allows the system to achieve high efficiency under good conditions while maintaining adaptability when conditions change
Solution Approach 2:
The RA procedure is designed to be dynamic, allowing the UE to switch between CFRA-based procedures (when configured and conditions permit) and CBRA-based procedures (when needed). The UE can dynamically select between different RA types based on the availability of CFRA resources and channel conditions, ensuring both efficiency and adaptability across varying operational scenarios
Data Source
AI summary
A method performed by a User Equipment (UE) for Beam Failure Recovery (BFR) is provided. The method includes the UE detecting a beam failure event on a serving cell, and initiating a Random Access (RA) procedure for BFR on a Bandwidth Part (BWP) of the serving cell. The RA procedure for BFR includes performing an RA type selection after determining that the UE is not configured with any Contention-Free RA (CFRA) resource for BFR, the RA type selection including determining a 2-step RA type or a 4-step RA type as an RA type of the RA procedure for BFR based on a Reference Signal Received Power (RSRP) value of a Downlink (DL) pathloss reference, skipping performing the RA type selection after determining that the UE is configured with a CFRA resource for BFR, and determining the RA type as the 4-step RA type after skipping the RA type selection.